Schendel and Wells have disclosed an enzymatic process for preparing [.gamma.-.sup.32 P]-adenosine triphosphate (ATP) with high specific activity. J. Biol. Chem. 248, 8319-8321 (1973). They used D-glyceraldehyde-3-phosphate as the starting material and employed oxidizing dyes for regeneration of NAD.sup.+ from NADH. D-glyceraldehyde-3-phosphate is available commercially only as the diethylacetal. For use in the process of Schendel and Wells, the diethylacetal must first be hydrolyzed and removed from the D-glyceraldehyde-3-phosphate. Moreover, unprotected D-glyceraldehyde-3-phosphate tends to be unstable and may have an objectionably short shelf-life.
Oxidizing dyes such as phenazine methosulfate and thiazolyl blue may interfere with subsequent enzyme reactions. For example, where the [.gamma.-.sup.32 P]nucleoside triphosphate is converted by further enzyme reactions to other [.sup.32 P]-labeled nucleotides, such as [.alpha.-.sup.32 P]-nucleotides, the intermediate [.gamma.-.sup.32 P]-nucleotide may have to be recovered from the reaction mixture, and then subjected to the additional reactions.
Commercially, the [.gamma.-.sup.32 P]-labeled nucleotides such as [.gamma.-.sup.32 P]-ATP and -dATP have also been prepared by enzymatic processes. However, the products of these processes have not been produced in as high yield and/or as high a specific activity as with the method described herein. Moreover, a more efficient enzymatic system would be very desirable, especially if the process could also be adapted as the first stage of a continuing process for producing other [.sup.32 P]-labeled nucleotides.